Tuesday, January 1, 2013

The Stratus Sandwich

It was worth a trip to the mountains today just to check out the various cloud layers.  At low levels, we had a deep cold pool entrenched over the Salt Lake Valley that was topped by stratus clouds that tongued their way up Little Cottonwood Canyon.

Looking west down Little Cottonwood Canyon @ 2:37 PM MST
1 Jan 2013.  Click to enlarge.
Above the cold pool, there was a layer with strong northerly flow and an altostratus cloud deck at mountaintop level.  The altostratus was widespread in the morning, forming a sort of "stratus sandwich," but became more broken during the afternoon.  During this period, the clouds lingered over the west-east oriented ridges, with clearing where the crest-level flow was sinking into Little Cottonwood Canyon, as depicted above.

The deep valley cold pool is actually a good thing.  During bad inversion events, the inversion is located very near the valley floor and all our pollution is confined to a very shallow layer.  Today, however, the inversion was located about 3000 feet above the valley floor, which is why there are stratus clouds tonguing so far up Little Cottonwood.  That means our pollution is being distributed through a deeper layer.  Unfortunately, the inversion will be lower and the air pollution worse later this week.

Also, there's not much hope for snow in the 7-day forecast.  Time to start appeasing the gods...

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